1. Field of the Invention
The present invention relates to a method for producing a photovoltaic cell.
2. Description of the Related Art
In the producing of a photovoltaic cell having a pn conjunction in the related art, for example, a p-type impurity is diffused into an n-type semiconductor substrate formed of silicon or the like and thereby a p-type diffusion layer is formed. Accordingly, the pn conjunction is formed.
Particularly, as a structure of photovoltaic cell for increasing conversion efficiency, a selective emitter structure, in which the impurity concentration in a region other than the region directly under an electrode is made to be lower than the impurity concentration in the region directly under the electrode, is disclosed (for example, refer to L. Debarge, M. Schott, J.C. Muller, R. Monna, Solar Energy Materials & Solar Cells 74 (2002) 71-75). In the structure, since the region in which the impurity concentration is high is formed directly under the electrode (hereinafter, the region is referred to as “selective emitter”), the contact resistance between a metallic electrode and the silicon can be reduced, on the other hand, in regions other than the region directly under the metallic electrode, the impurity concentration is low, such that it is possible to improve the conversion efficiency of the photovoltaic cell.
To form the selective emitter structure described above, there is necessary a complicated process in which plural diffusions and partial etching through masking or the like are repeated (for example, refer to Japanese Patent Application Laid-Open (JP-A) No. 2004-193350).
In addition, a method in which a diffusing agent is applied onto a substrate with a plurality of impurity concentrations through an ink jet method, and impurities are diffused is disclosed (for example, refer to JP-A No. 2004-221149).